The use of dead bolts for security purposes is widespread. One example of a high security dead bolt lock is shown in U.S. Pat. No. 7,007,524 (Lockmasters, Inc., Nicholasville, Ky.), the disclosure of which is incorporated herein by reference. Another example of these types of dead bolt mechanisms is shown in U.S. Pat. No. 7,424,814 (Lockmasters, Inc.), the disclosure of which is also incorporated by reference herein. These systems include various mechanisms that prevent retraction of the dead bolt, including a typical lock with a lock bolt and at least one electronic, internal access control that may be actuated by entering correct code or credential. These systems include a handle on the outside of the door that is operable to retract the dead bolt provided that the lock and access member(s) are unlocked. These systems may or may not include a life safety feature in the form of an escape lever that allows a user to retract the dead bolt from an inside of the door regardless of the status of the lock and/or the access control mechanism(s). Moreover, these systems include several security features that thwart unwanted entry, such as a night latch lock down mechanism that disables the internal mechanisms responsible for retracting the dead bolt when the outside handle is actuated. Additionally, several mechanical features are provided that block internal dead bolt retraction mechanisms in case the system is tampered with.
Despite the success of these systems, there are drawbacks associated with these systems and other prior art in the lock industry. The complicated designs of the multiple security features lend themselves to complicated assembly and re-assembly after, for example, a relock mechanism has been triggered, whether accidentally or after a thwarted attempt. The use of the lock down mechanism adds to the complication of the design and prevents the use of a panic bar on the inside of the door. Moreover, malfunctioning of the lock down mechanism may prevent the escape lever from functioning. And, because the override mechanism is configured to override each of the lock and access member(s), there is a risk that, if the override key is obtained by an unwanted person, access to the secure area is very likely to occur.
Moreover, there is no indication to a user on the inside of the door whether the dead bolt is in an extended or retracted position. This may be problematic because it is possible that an authorized person trying to gain access to the secure area may arrange to have the deadbolt blocked from re-extending upon closing of the door. Such blocking may be completed in many ways, such as by inserting an object into or disabling a certain structure in the system to prevent the passage or movement of the dead bolt once the door closes. In an ordinary door, a person may be able to view whether the dead bolt is extended by viewing the space between an edge of the door and the doorjamb. However, in high security environments, a space between the door jamb and door may not be visible due to sound sealing insulation or other materials or structure, making it impossible to see whether the dead bolt is in the extended or retracted position. These systems include dead bolt hold back mechanisms that prevent the dead bolt from extending when the door is open. Moreover, because the escape lever is operative to retract the dead bolt upon actuation of the escape lever, opening the door from the inside with the escape lever or from the outside with the handle to check the status of the dead bolt will not provide an indication of tampering.
In view of these and other challenges in this area of the lock industry, a need has developed to provide an improved dead bolt lock system.